Microelectronic structures, such as interconnect or metallization layers, may be manufactured by depositing consecutive layers of materials on a substrate. Depending upon the fabrication techniques and materials, one or more of these consecutive layers may form a nonplanar surface having uneven topography. It may be desirable to planarize nonplanar topographies in preparation for subsequent depositions or operations. Most commonly, planarization techniques such as chemical mechanical planarization (“CMP”) are utilized to produce a substantially planar surface across adjacent exposed materials, such as alternating metallized interconnect layers and interlayer dielectric layers.
In some manufacturing scenarios, it is desirable to obtain nonplanar topographies having controlled tolerances for relative protrusion of various materials. For example, to utilize diffusional creep as a facilitating factor for conductive layer interfacing purposes as described in a co-filed and co-assigned U.S. patent application for the invention entitled “Method and Structure for Interfacing Electronic Devices”, it is desirable to manufacture structures wherein a series of metal layers extends, or protrudes, away from the surrounding substrate material, as in the structure depicted in FIG. 2B, which is discussed in further detail below. To form such a configuration, a technique for selectively removing substrate material is useful. Such a method may comprise removing substrate material at a significantly greater rate than that at which metal layer material is removed, or it may comprise removing substrate material without removing substantially any of the metal layer material. The selectivity of conventional etchants to certain groups of materials as opposed to other groups provides the opportunity for selective etching where materials are appropriately paired. For example, conventional wet etchants may be utilized to selectively etch a silicon dioxide substrate at a faster rate than that at which adjacent copper metal layers are etched. Conventional patterning techniques may also be utilized to facilitate selective etching of substrate materials between metal layers, using anisotropic plasma etch chemistries and techniques, for example. These methods generally add complexity to structure processing, and may be somewhat imprecise. Further, in the event that a required surface is to have more than one level of topography, such as a surface wherein certain groups of metallized layers are to protrude farther from the adjacent substrate material than are other metallized layers within the same surface, in effect requiring several different echelons of substrate height relative to the height of metallized layers, current processes are nonideal.
There is a need for a relatively streamlined process to manufacture structures wherein the protrusion height of metal layers relative to intermetal substrate layers may be controllably adjusted. Further, there is a need for a process to controllably form surfaces having multiple tiers or echelons of topography.